Film on boiled tea, very cloudy, tastes thick - help!

I have been making tea for 42 years. I'm from Texas and was taught to boil it, let it cool, add sugar and water, put in pitcher in fridge. I've made tea under every circumstance - different pots, different brands, etc. Every once in a while I would get an icky batch but for 2 or 3 weeks almost every pot I make gets a film on top and turns cloudy. It also tastes awful. I have boiled it less, heated it in the microwave, used different tea bags and a different pot. I cannot understand why this is happening. Any ideas?